The present invention relates to a mobile communications system, and more particularly to a method for reducing call loss in a mobile communications system that registers mobile user codec types in a database in a mobile network, and conducts protocol negotiation using the codec types.
In a conventional mobile communications system, the registration of a mobile user codec type into a location register, a database in a mobile network, is conducted on the premise that a mobile communication carrier executes it through a maintenance control line in response to a request from a user.
This will be explained with reference to FIG. 1. In FIG. 1, a user 1 notifies a carrier of the change of his or her mobile station, that is, the change of a codec type, through a certain communication means like a postal card. A system operator (SO) of the carrier registers through a terminal 3 the change of the mobile station by the user, that is, the change of the codec type, into a home memory station 4 including a location register (database) that registers the current location of the mobile station. Thus, the change of the mobile station by the user 1, the change of the codec type, is registered in a mobile network system side (switching system/switching center side) 2 (refer to xe2x80x9ca code matching methodxe2x80x9d disclosed in Japanese Patent Application No. 4-55267 (Laying-open No. 6-6295) assigned to the same assignee of the present application).
Conventionally, the mobile user codec types are registered in the location register, the database, in a home memory station that registers the locations or the like. Such a registration method, however, has a problem in that it takes a rather long time to update the registration because the carrier conducts the registration using the maintenance control processing at the request of the user. This sometimes causes a discrepancy between the mobile station the user actually uses and the information in the location register, thereby resulting in a call loss.
Furthermore, the call loss also takes place when a codec out of service by the mobile network is decided in the negotiation conducted between the mobile network and the mobile station when a plurality of codecs are assigned to the mobile station, and one of them is to be selected. This will be described with reference to FIG. 2.
In FIG. 2, a location register 41 in the home memory station 4 stores two codecs P1 and P2 selectable by a mobile station 11. However, a visitor location switching system (switching center) 5 associated with the current location of the mobile station 11 offers a service of only the codec P2. When a mobile station 12 calls the mobile station 11 in this state, the negotiation for selecting the codec begins between the calling mobile station 12 and the mobile network.
During the negotiation, the calling mobile station 12 calls the mobile station 11. The location register 41 associated with the mobile station 11 registers that the mobile station 11 can select one of the codec types P1 and P2. It reads them, and notifies the calling mobile station of them (1). Since the mobile station 12 can also select one of the codecs P1 and P2, it selects P1 as the codec (2), and tries to establish a channel with the mobile station 11 in the mobile network (3). However, since the visitor location switching system 5 associated with the current location of the mobile station 11 does not support the codec P1, it cannot provides the service, resulting in the call loss.
An object of the present invention is to achieve quick registration for updating the mobile user codec type into the location register (database) to maintain consistency of data between users and a mobile network side.
Another object of the present invention is to prevent the call loss due to the discrepancy between the codec types available by the network side and the codec type selected as described above.
There is provided a mobile communications system including a mobile station and a database of a network which registers a location of the mobile station, wherein the mobile station notifies, when it conducts mobile station location registration or when a mobile user replaces an old mobile station, the mobile network of one or more codec types supported by the mobile station; and the database of the network updates registered codec types using the codec types notified.
Using the mobile communications control signal makes it possible to quickly achieve the update of the codec types of the mobile station in the database in the mobile network, and to maintain the consistency of the data between the user side and the network side.
Here, the mobile network may comprise a switching center interposed between the mobile station and the database; and the switching center may transfer to the database only a codec type supported by the switching center among the codec types sent from the mobile station.
Since only the codec types the mobile network associated with the current location of the mobile station are entered into a location register from among the codec types supported by the mobile station, the call loss such as described above can be eliminated.
The mobile station can notify the mobile network of the codec types by adding them to the location registration request, or independently of the location registration request.
One aspect of the present invention includes a mobile station in the mobile communication system.